Engineering Highly Active Brookite Titania Nanorods for Sustainable Hydrogen Production

Titanium dioxide (TiO₂, titania) nanomaterials are the most studied photocatalysts because of their abundancy, non-toxicity, stability and activity. Anatase and rutile polymorphs have been deeply investigated because they are the energetically favored forms at the nanoscale and in the bulk, respectively. Brookite, instead, has been rarely studied, despite theoretical and experimental data support its higher activity in some photocatalyzed transformations. By taking advantage of methods to produce 1-D phase-pure brookite nanorods, we show not only that brookite is a much more active photocatalyst than anatase, but also that its activity is length-dependent. In particular, we attribute the high activity to both the 1-D nature of the nanostructure, which favors electron-hole separation, and to the defective structure of the rods, which are subject to strain that causes favorable changes in electron-hole recombination processes. By tuning length and strain we are able to prepare samples that show among the highest rates of hydrogen production from biomass-derived compounds under solar simulated irradiation reported to date.